This invention relates to high-intensity-discharge (HID) sodium-vapor lamps and, more particularly, to HID sodium-vapor lamps which utilize a relatively high fill pressure of xenon and a particular trigger electrode construction to facilitate starting.
U.S. Pat. No. 3,248,590 dated Apr. 26, 1966 to Schmidt broadly discloses HID sodium-vapor lamps and in FIG. 4 thereof discloses the effect of varying the xenon fill pressure from 0 to 300 torrs, when the discharge sustaining material is sodium per se. In the bridging paragraph between columns 7 and 8 of this patent and the first full paragraph in column 8 is disclosed the addition of mercury as a discharge-sustaining substance.
U.S. Pat. No. 3,384,798 dated May 21, 1968 to Schmidt discloses the use of sodium-mercury amalgam as a discharge-sustaining filling along with xenon starting gas at a fill pressure of 20 torrs.
In U.S. Pat. No. 3,721,845 dated Mar. 20, 1973 to Cohen et al. is disclosed the use of a heater wire wrapped around an insulating rod which is closely spaced to the arc tube portion of an HID sodium lamp. Once the lamp starts, the heater is disconnected from the circuit by means of a thermal switch. A starting aid in the form of wire loops extends between the electrodes and these wire loops are carried proximate the exterior surface of the arc tube.
In U.S. Pat. No. 3,746,914 dated July 17, 1973 to Olson et al. is disclosed a tungsten resistance heater coiled about the arc tube in order to facilitate starting. After the lamp is started, the heater is cut out by means of a thermal switch.
U.S. Pat. No. 3,757,158 dated Sept. 4, 1973 to Kopelman discloses a sodium-vapor lamp arc tube having a spiral groove on the outer surface thereof with a heater wire carried within the spiral groove. Once the lamp is started, the heater wire is cut out of the circuit by means of a thermal switch.
In U.S. Pat. No. 3,757,159 dated Sept. 4, 1973 to Gutta et al. is disclosed a starting aid heater carried in a ceramic tube positioned proximate and exterior to an arc tube. An additional starting aid in the form of a fine wire encircles and is coiled about the arc tube and the ceramic sleeve.
U.S. Pat. No. 3,755,708 dated Aug. 28, 1973 to Audesse discloses an external heater spaced proximate an arc tube with a heater coiled about an insulating support. Once the lamp has started, the heater wire is removed from the circuit by means of an external switch.
U.S. Pat. No. 3,900,753 dated Aug. 19, 1975 to Richardson discloses a loop starting aid wrapped around the arc tube and a gas fill within the arc tube of a Penning mixture. A thermal switch removes the loop starting aid from circuit after the lamp is started.
U.S. Pat. No. 4,037,129 dated July 19, 1977 to Zack et al. discloses a multiple turn wire starting aid wound about an arc tube and extending longitudinally along the arc tube for a distance that is at least 10 percent of the arc tube length. The wire starting aid electrically connects to one of the electrodes and is removed from the circuit after the lamp is operating by a heat actuated switch. The arc tube utilizes a Penning gas mixture to facilitate starting.